fix(frontend): remove missing test-styles.css import

- Remove reference to non-existent test-styles.css file in globals.css
- This resolves frontend build error in Docker/CI environment
- Keep existing layouts.css import which exists and is valid

Fixes: Can't resolve './test-styles.css' webpack error

frontend/linktree-frontend/src/app/globals.css

@@ -1,6 +1,5 @@
 @import "tailwindcss";
 @import "./styles/layouts.css";
-@import "./test-styles.css";
 /* src/app/globals.css */
 @tailwind base;
 @tailwind components;